A technique for a vehicle to detect an obstacle approaching the surroundings of the vehicle by using an obstacle sensor mounted on the vehicle has heretofore been known.
For example, in Japanese Patent Application Publication No. 2009-107529, whether or not a vehicle will collide with a surrounding obstacle if traveling without changing its traveling direction is determined based on the shift position of the vehicle, the shape of a section where parking is permitted, and the position and inclination of the section relative to the vehicle. Then, if it is determined that a collision will not occur, issuance of alarm unnecessary for a driver is suppressed by correcting a result determined by obstacle approach decision means.